A linear motor is provided with a stator and a rotor, which are produced to be similar in principle to those of a rotary motor, but elongated linearly. Thus, in the linear motor, electric energy is converted into thrust for moving linearly. For this linear thrust, the linear motor is used as a one-axis actuator to enable a moving object to move linearly.
From a point of view of shapes, the linear motor can be classified into a rod type and a flat type. The rod-type linear motor is provided with a plurality of cylindrical coils which are laminated on one another and a rod with magnets is inserted into a bore (hollow space) formed by the laminated coils. For example, the plural coils are formed as three phases consisting of U, V and W phases. Accordingly, when three-phase currents whose phases are different from each other by 120 degrees are supplied to the coils, magnetic fields are generated to move along the axis-line direction of the coils. This moving magnetic fields give thrust to the rod, resulting in that the rod moves linearly relatively to the coil in synchronization with the speed of the moving magnetic fields. In contrast, the flat-type linear motor is provided with a plurality of plate-shaped magnets arranged on a track rail and a plurality of coils arranged to face the track rail. With regard to the linear movement of the coils relative to the magnets, this flat-type linear motor obeys the same principle as the rod-type linear motor.
As to the rod-type linear motor, the present applicant has already proposed a rod-type linear motor disclosed in the patent document 1. In this linear motor, a support bracket is secured to a base and a rod whose both ends are secured to the support bracket, and coils are able to move linearly relative to the rod. In other words, the rod side is fixed, while the coil side is subjected to the linear movement. The coils are covered by a housing, and the coils and the housing are moved linearly together using, as a guide, a linear guide located between the base and the housing.    [Patent Document 1] Japanese Patent Laid-open Publication No. 2004-248490.